Rename CollectionIndexCache API to not use 'Element'

Source/core/dom/ChildNodeList.h

Index: Source/core/dom/ChildNodeList.h
diff --git a/Source/core/dom/ChildNodeList.h b/Source/core/dom/ChildNodeList.h
index 88c779e8ac6486837890a0f4ef16bb9bdac45960..c3b8ffbf5dd9636fba4ab092373a8e3e2943fe79 100644
--- a/Source/core/dom/ChildNodeList.h
+++ b/Source/core/dom/ChildNodeList.h
@@ -53,8 +53,8 @@ public:
 
     // CollectionIndexCache API.
     bool canTraverseBackward() const { return true; }
-    Node* traverseToFirstElement() const { return rootNode().firstChild(); }
-    Node* traverseToLastElement() const { return rootNode().lastChild(); }
+    Node* traverseToFirst() const { return rootNode().firstChild(); }
+    Node* traverseToLast() const { return rootNode().lastChild(); }
     Node* traverseForwardToOffset(unsigned offset, Node& currentNode, unsigned& currentOffset) const;
     Node* traverseBackwardToOffset(unsigned offset, Node& currentNode, unsigned& currentOffset) const;